Halloysite nanotubes functionalized with a nanocomposite prepared from reduced graphene oxide and polythiophene as a viable sorbent for the preconcentration of six organochlorine pesticides prior to their quantitation by GC/MS

The authors describe a method for dispersive microsolid phase extraction (d-mu SPE) coupled to gas chromatography and mass spectrometry for the preconcentration and determination of the organochlorine pesticides aldrin, dicofol, DDE, endosulfan, dieldrin, and DDT in samples of herbal distillates. The hybrid nanocomposite was obtained by bonding halloysite nanotubes to reduced graphene oxide and loading it with polythiophene. The nanocomposite (typically 5 mg) is dispersed in a syringe and employed as an extraction device. The analytes are adsorbed on the solid sorbent and then desorbed with organic solvent. Solvent type and volume, extraction time, sorbent amount, effect of pH values, salt concentration and matrix effect on the extraction efficiency were investigated. Under the optimal conditions, the limits of detection (at an S/N ratio of 3) are in the range between 2 and 13 ng L-1 for the six organochlorine pesticides, and the linearity extended from 0.1 to 100 mu g L-1, and from 0.1 to 200 mu g L-1 (two ranges). The method precision (RSD) is in the range of 6.1-8.7% (intra-day; for n = 5), and of 6.3-9.7% (inter-day, for n = 5). The obtained recoveries of nearly all analytes from spiked herbal distillates samples are between 72.3 and 110.7%.